The invention relates to a finely pulverized component added in vehicle spray washing water, and more particularly for sprayingly washing out the so-called "last one film" formed on the car body surface without necessity of manual scrubbing or brushing. Further it relates to a vehicle spray washing system comprising an apparatus for recovering said finely pulverized component from waste washing water.
A car body is inevitably covered with minute dirt particles of soil, worn tire and pavement materials, dust in exhausted gas and the like bonded together and adhered on the coating surface by oily content in the atmosphere originated from incompletely combustioned fuel and asphalt, during driving. The dirt film may be washed out by spraying water generally added with a detergent such as a surface active agent, so far as the upper layer thereof is concerned.
The lower layer generally formed with more finely pulverized materials, however, can not be always readily washed out by the usual spray car washing apparatus which discharge pressure at less than 100 kg/cm.sup.2, generally in ranges from 30 to 70 kg/cm.sup.2. The pressure range avoids possible damage formed on the surface coating and further any other danger. Such layer is, thus, often called the "last one film", which is considered to firmly adhere on the car body surface due to van der Waals force between the minute dirt particles with each other and the body surface, static electricity and surface tension of water present in gaps formed therebetween. This last one film may be formed unexpectedly in a short time, e.g. by one day drive, which is of course varied depending on driving circumstances. As time lapses, the dirt particles are rapidly deposited thereon when the last one film is left without washing. In overcrowded conditions frequent car washings are required.
Another reason why the last one film can not be removed only by spray washing that sprayed water forms a static water sublayer on the coating surface independent from a dynamic water flow so as to protect the last one film, which may well explain the reason why manual scrubbing or brushing washing can fairly readily remove such last one film.
In order to avoid such labour and time consuming manual scrubbing or brushing, a roll-over type car washing machine has been proposed and actually used, which is provided with nozzles for spraying water with many rotatable brushes and adapted to move as a whole relative to the car. This washing machine is, however, generally disliked by drivers because the brushes sometimes hurt the coating surface of the car to form the so-called brush marks which are conspicuous particularly on the surface coated in black, red or blue and may eventually break protruding parts such as mirrors, wipers and antennas, while recessed portions can not be sufficiently washed.
Chemical washing which uses a strong alkaline or acidic chemical, it is also not liked in that such chemicals may discolor the coating and corrode various metal parts of the car and further cause the environmental problem of disposing of waste washing water.
It is noted here that there is another nature of dirt of the car body surface, which is called "stains" and formed by deterioration of wax and/or dirt infiltration in fine cracks or pinholes of the coating, and conspicuous on the body surface coated in white, already in several months, which are varied depending on the driving circumstances of the car. This can be removed by said roll-over type washing machine or said chemical washing, but the disadvantages referred to above must be expected.
In order to avoid such defects, JP-A Sho 61(1986)-190599 has proposed to spray water for washing which is added with pulverized abrasive such as diatomaceous earth, talc, zeolite, calcium carbonate, bentonite, kaolin and dolomite having particle size of 0.1-5 .mu.m and Mohs' hardness of less than 6. This method is useful for removing "stains" every two to four months, but useless for removing "last one film", since the relatively hard pulverized abrasive is liable to hurt the coating when it collide thereagainst during the spray washing. Furthermore, such pulverized abrasive is disadvantageous in that it cannot be easily separated from the sludge or the like removed from the body surface during washing, due to its specific gravity of the value larger than 1, and therefore, it is difficult to recover the same for reuse.